After fixing the controller not found exception following our client's recent upgrade to Web Forms for Marketers 8.1, all of our forms continued to throw an exception on load: Compilation Error. CS0104: 'Constants' is an ambiguous reference between 'Sitecore.
We recently upgraded one of our clients from Sitecore 8.0 to Sitecore 8.1 and had to upgrade to Web Forms for Marketers 8.1 rev. 160304 as part of the upgrade. After upgrading WFFM, all of our forms